red.cpp: In constructor 'BigNumber::BigNumber(std::string)': red.cpp:71: warning: comparison between signed and unsigned integer expressions red.cpp: In function 'int main()': red.cpp:270: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result red.cpp:270: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result